Public Network Connectivity

[vyzo]

Performs the necessary work to support the public Internet. Closes #11

Summary:

• mcnode and mcdir now bind to INADDR_ANY
• mcnode allows NAT configuration:
  • none; default, no NAT
  • auto; use the libp2p NATPortMap service
  • manual; uses a user specified public address
• mcnode is selective in how it reports addresses to the directory:
  • if the directory is on localhost, then it reports its localhost address; supports testing
  • if the directory is on a private network, then it will publish its routable addresses
  • if the directory is on a publicly routable network, then it will only report public addresses (if any)
• mcnode configuration is now persisted to disk.

Tested on laptop and ec2.

[parkan]

lgtm